[PATCH 1/9] workqueue: devres: Add device-managed allocate workqueue

[Krzysztof Kozlowski]

Add a Resource-managed version of alloc_workqueue() to fix common
problem of drivers mixing devm() calls with destroy_workqueue.  Such
naive and discouraged driver approach leads to difficult to debug bugs
when the driver:

1. Allocates workqueue in standard way and destroys it in driver
   remove() callback,
2. Sets work struct with devm_work_autocancel(),
3. Registers interrupt handler with devm_request_threaded_irq().

Which leads to following unbind/removal path:

1. destroy_workqueue() via driver remove(),
   Any interrupt coming now would still execute the interrupt handler,
   which queues work on destroyed workqueue.
2. devm_irq_release(),
3. devm_work_drop() -> cancel_work_sync() on destroyed workqueue.

devm_alloc_workqueue() has two benefits:
1. Solves above problem of mix-and-match devres and non-devres code in
   driver,
2. Simplify any sane drivers which were correctly using
   alloc_workqueue() + devm_add_action_or_reset().

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxxxxxxxx>

---

All further patches depend on this one.
---
 Documentation/driver-api/driver-model/devres.rst |  7 ++++++
 include/linux/workqueue.h                        | 32 ++++++++++++++++++++++++
 kernel/workqueue.c                               | 32 ++++++++++++++++++++++++
 3 files changed, 71 insertions(+)

diff --git a/Documentation/driver-api/driver-model/devres.rst b/Documentation/driver-api/driver-model/devres.rst
index 7d2b897d66fa..dfc1e85ebfaa 100644
--- a/Documentation/driver-api/driver-model/devres.rst
+++ b/Documentation/driver-api/driver-model/devres.rst
@@ -464,3 +464,10 @@ SPI
 
 WATCHDOG
   devm_watchdog_register_device()
+
+WORKQUEUE
+  devm_alloc_workqueue()
+  devm_alloc_ordered_workqueue()
+  devm_create_workqueue()
+  devm_create_freezable_workqueue()
+  devm_create_singlethread_workqueue()
diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index a4749f56398f..583b0c4bd55c 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -512,6 +512,26 @@ __printf(1, 4) struct workqueue_struct *
 alloc_workqueue_noprof(const char *fmt, unsigned int flags, int max_active, ...);
 #define alloc_workqueue(...)	alloc_hooks(alloc_workqueue_noprof(__VA_ARGS__))
 
+/**
+ * devm_alloc_workqueue - Resource-managed allocate a workqueue
+ * @dev: Device to allocate workqueue for
+ * @fmt: printf format for the name of the workqueue
+ * @flags: WQ_* flags
+ * @max_active: max in-flight work items, 0 for default
+ * @...: args for @fmt
+ *
+ * Resource managed workqueue, see alloc_workqueue() for details.
+ *
+ * The workqueue will be automatically destroyed on driver detach.  Typically
+ * this should be used in drivers already relying on devm interafaces.
+ *
+ * RETURNS:
+ * Pointer to the allocated workqueue on success, %NULL on failure.
+ */
+__printf(2, 5) struct workqueue_struct *
+devm_alloc_workqueue(struct device *dev, const char *fmt, unsigned int flags,
+		     int max_active, ...);
+
 #ifdef CONFIG_LOCKDEP
 /**
  * alloc_workqueue_lockdep_map - allocate a workqueue with user-defined lockdep_map
@@ -568,19 +588,31 @@ alloc_workqueue_lockdep_map(const char *fmt, unsigned int flags, int max_active,
  */
 #define alloc_ordered_workqueue(fmt, flags, args...)			\
 	alloc_workqueue(fmt, WQ_UNBOUND | __WQ_ORDERED | (flags), 1, ##args)
+#define devm_alloc_ordered_workqueue(dev, fmt, flags, args...)		\
+	devm_alloc_workqueue(dev, fmt, WQ_UNBOUND | __WQ_ORDERED | (flags), 1, ##args)
 
 #define create_workqueue(name)						\
 	alloc_workqueue("%s", __WQ_LEGACY | WQ_MEM_RECLAIM | WQ_PERCPU, 1, (name))
+#define devm_create_workqueue(dev, name)				\
+	devm_alloc_workqueue(dev, "%s", __WQ_LEGACY | WQ_MEM_RECLAIM | WQ_PERCPU, 1, (name))
+
 #define create_freezable_workqueue(name)				\
 	alloc_workqueue("%s", __WQ_LEGACY | WQ_FREEZABLE | WQ_UNBOUND |	\
 			WQ_MEM_RECLAIM, 1, (name))
+#define devm_create_freezable_workqueue(dev, name)			\
+	devm_alloc_workqueue(dev, "%s", __WQ_LEGACY | WQ_FREEZABLE | WQ_UNBOUND |	\
+			     WQ_MEM_RECLAIM, 1, (name))
+
 #define create_singlethread_workqueue(name)				\
 	alloc_ordered_workqueue("%s", __WQ_LEGACY | WQ_MEM_RECLAIM, name)
+#define devm_create_singlethread_workqueue(dev, name)			\
+	devm_alloc_ordered_workqueue(dev, "%s", __WQ_LEGACY | WQ_MEM_RECLAIM, name)
 
 #define from_work(var, callback_work, work_fieldname)	\
 	container_of(callback_work, typeof(*var), work_fieldname)
 
 extern void destroy_workqueue(struct workqueue_struct *wq);
+extern void devm_destroy_workqueue(struct device *dev, void *res);
 
 struct workqueue_attrs *alloc_workqueue_attrs_noprof(void);
 #define alloc_workqueue_attrs(...)	alloc_hooks(alloc_workqueue_attrs_noprof(__VA_ARGS__))
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 72a8b64188b3..fd840c46ba55 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -41,6 +41,7 @@
 #include <linux/mempolicy.h>
 #include <linux/freezer.h>
 #include <linux/debug_locks.h>
+#include <linux/device/devres.h>
 #include <linux/lockdep.h>
 #include <linux/idr.h>
 #include <linux/jhash.h>
@@ -5895,6 +5896,31 @@ struct workqueue_struct *alloc_workqueue_noprof(const char *fmt,
 }
 EXPORT_SYMBOL_GPL(alloc_workqueue_noprof);
 
+__printf(2, 5) struct workqueue_struct *
+devm_alloc_workqueue(struct device *dev, const char *fmt, unsigned int flags,
+		     int max_active, ...)
+{
+	struct workqueue_struct **ptr, *wq;
+	va_list args;
+
+	ptr = devres_alloc(devm_destroy_workqueue, sizeof(*ptr), GFP_KERNEL);
+	if (!ptr)
+		return NULL;
+
+	va_start(args, max_active);
+	wq = alloc_workqueue(fmt, flags, max_active, args);
+	va_end(args);
+	if (wq) {
+		*ptr = wq;
+		devres_add(dev, ptr);
+	} else {
+		devres_free(ptr);
+	}
+
+	return wq;
+}
+EXPORT_SYMBOL_GPL(devm_alloc_workqueue);
+
 #ifdef CONFIG_LOCKDEP
 __printf(1, 5)
 struct workqueue_struct *
@@ -6025,6 +6051,12 @@ void destroy_workqueue(struct workqueue_struct *wq)
 }
 EXPORT_SYMBOL_GPL(destroy_workqueue);
 
+void devm_destroy_workqueue(struct device *dev, void *res)
+{
+	destroy_workqueue(*(struct workqueue_struct **)res);
+}
+EXPORT_SYMBOL_GPL(devm_destroy_workqueue);
+
 /**
  * workqueue_set_max_active - adjust max_active of a workqueue
  * @wq: target workqueue

-- 
2.51.0